Contributions from the Biological Laboratories in Princeton University Volume 5

Description

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1916 edition. Excerpt: ...into the veins (4, figs. 11 and 13). For the reason that the medial pharyngeal lymphatic is a structure of relatively greater importance in the embryos of ganoids than in those of the trout, the earliest stages of its de velopment are more easily followed in ganoids than in the trout. The earliest anlage of the medial pharyngeal lymphatic was met with in a 7.5 mm. embryo of Amia (6.81 mm., measured by sections) and is shown in section in figure 40. This anlage (4') was included in two sections (10 micra each) and, as shown in the figure, it neither communicates with the precardinal vein (6), nor is it connected with the latter in this, or in any other section, by a solid endothelial strand. A study of the later stages shows that this independent anlage invariably establishes a connection with the precardinal vein (4, figs. 12 and 13), and it can then be easily injected from the veins before lymphatico-venous valves are formed. The vascular system of the embryo from which figure 40 is taken was fully reconstructed in order to prove that the anlage in question was that of the medial pharyngeal lymphatic. Since this independent anlage was found to occupy identically the same relative position in this embryo as that of the medial pharyngeal sac of later stages, no possible doubt can exist regarding it. The anlagen of the lymphatic system, which develop in close relation to the typical points at which the lymphatics establish communications with the veins, have been described by Huntington and McClure ('10) in mammals as 'venolymphatics.' The term 'venolymphatic' may therefore be similarly applied to those anlagen of the lymphatic system of fishes which develop contiguous to the typical points at which the lymphatics communicate with the...show more